1. Technical Field
The present invention relates to a color toner for flash fusing processes, a process for forming the color toner, an electrostatic image developer, a process cartridge and an image forming apparatus.
2. Related Art
In electrophotographic processes commonly employed in copying machines, printers, printing machines, and the like, images are generally formed in the following manner: the photoconductive insulator surface of a photoreceptor drum is first uniformly charged positively or negatively (in a charging step), and then an electrostatic latent image is formed according to image information by irradiating, for example, a laser beam onto the photoconductive insulator surface and thus partially removing the electrostatic charge on the insulator surface. The latent image is then converted to a visible toner image, for example, by applying fine particles of a developer called toner onto the latent image area retaining the electrostatic charge on the photoconductive insulator. Generally, the toner image obtained in this manner is transferred electrostatically onto a recording medium such as recording paper and then the toner image is fixed on the recording medium in order to produce printed matter.
Various solidification and fusion methods including fusion of the toner by application of heat and/or pressure and fusion of the toner by photoirradiation energy have been used for fixing the toner image after transfer, and flash fusing processes utilizing light, which are advantageous compared with application of heat or pressure, are now attracting more attention. Examples of the flash fusing processes which have been known include a flash fixing process using a xenon lamp, a laser fixing process using a high-intensity laser.
That is, the flash fusing process, which demands no pressure for toner fixation, has an advantage that the resolution (reproducibility) of the toner image is less deteriorated in the fixing step because the image needs not be brought into contact (or pressurized) with, for example, a fixing roller. In addition, such a device allows printing immediately after it is turned on, because it demands no preheating of heat sources such as a fixing roller and thus eliminates the waiting time for the heat sources to be preheated to a desired temperature after it is turned on. Elimination of the high-temperature heat sources is also advantageous in effectively preventing the rise in temperature of the device and in preventing the ignition of recording paper due to the heat from the heat sources even when the recording paper clogs in the fixing device due to system malfunction.
However, when color toners are used for fixing, the flash fusing process is rather lower in fixing efficiency than when a black toner is used, because of the lower light absorption efficiency of the color toners.
Known infrared absorbers for toners have colors such as black, brown or green and may thus exert significant influence on a tone of a toner to which the infrared absorbers are added to cause a fluctuation in a tone of an image obtained therewith after fixation.